Fa Cies and Fauna Prox Ies Used to Re Con Struct the MIS 5 and MIS 7 Coastal En Vi Ron Ments in East Ern Tu Ni Sia

Geo log i cal Quar terly, 2017, 61 (1): 186–204 DOI: http://dx.doi.org/10.7306/gq.1312 Fa cies and fauna prox ies used to re con struct the MIS 5 and MIS 7 coastal en vi ron ments in east ern Tu ni sia Amel CHAKROUN1, * and Dalila ZAGHBIB-TURKI1 1 Uni ver sity of Tu nis El Manar, De part ment of Ge ol ogy, Fac ulty of Sci ences of Tu nis, Uni ver sity Cam pus, 2092, El Manar II, Tu ni sia Chakroun, A., Zaghbib-Turki, D., 2017. Fa cies and fauna prox ies used to re con struct the MIS 5 and MIS 7 coastal en vi ron - ments in east ern Tu ni sia. Geo log i cal Quar terly, 61 (1): 186–204, doi: 10.7306/gq.1312 This study is based on the anal y sis of the sedimentology and the fos sil as sem blages of Pleis to cene de pos its in East ern Tu ni - sia. It uses dif fer ent fauna as sem blages to help in fer palaeoenvironments and in par tic u lar dis cusses the im por tance of the dis tri bu tion of Persististrombus latus, es pe cially as re gards MIS 5e de pos its around the Med i ter ra nean Ba sin. The strati - graphic suc ces sion has been di vided into two main units. The lower unit is quartz-rich. Its basal part con tains a ma rine fauna that in cludes well-pre served bi valves, gas tro pods, echinoids and cirripedes dom i nated by Acanthocardia, Cerastoderma, Parvicardium, Arca, Donax, Glycymeris, Loripes, Tellina and Cerithium. This fauna rep re sents a typ i cal as so ci a- tion/biocenosis typ i cally de vel oped in a shel tered bay, of mod er ate to low wave/cur rent ac tion and rapid post-mor tem burial. The up per unit is car bon ate-dom i nated. Its basal part also con tains a rich ma rine fauna that in cludes the ex tant trop i cal West Af ri can spe cies Persististrombus latus. The oc cur rence of Persististrombus latus in this unit com pared to its pres ence in the whole Med i ter ra nean ba sin in the Late Pleis to cene leads us to ques tion its im por tance in the in ter pre ta tion of cli mate warm - ing dur ing the Late Pleis to cene, and to sug gest its At lan tic or i gin. Key words: MIS 5 and MIS 7, Tu ni sia, malacofauna, palaeo ec ol ogy, Persististrombus latus, palaeoclimate. INTRODUCTION ties help to re con struct their depositional en vi ron ments or biotopes de vel oped along the east ern coast of Tu ni sia. Pleis to cene de pos its of the east ern coast of Tu ni sia cor re la - tive to ma rine iso tope stage (MIS) 5, MIS 7 and MIS 9 have been MATERIAL AND METHODS the sub ject of sev eral stud ies (Allemand-Mar tin, 1923, 1924; Castany, 1954, 1955, 1956; Barrot, 1972; Paskoff and Along the east ern Tu ni sian coast, from the Cap Bon to Sanlaville, 1976, 1977, 1978, 1980, 1983; Oueslati, 1980; Hergla ar eas, the Pleis to cene (MIS 5e and MIS 7) suc ces sion, Oueslati et al., 1982; Blanc, 1982; Bernat et al., 1985; Miller et out crop ping at the cit ies of Menzel Temime, Qorba and Hergla al., 1986; Mahmoudi, 1986, 1988; Oueslati, 1994; Jedoui, 2000; (Fig. 1), is in ves ti gated. Five sec tions across this suc ces sion Jedoui et al., 2001, 2002, 2003; Bouaziz et al., 2003; Le Guern, are de tailed (Fig. 2). In the study, the stra tig ra phy was doc u - 2005; Chakroun et al., 2005, 2009a, b, 2016; Chakroun, 2006; mented, and sam ples were col lected from the car bon ate and Mauz et al., 2009; Mejri et al., 2012). This suc ces sion, con tain ing the quartz-rich units (MT, Q2 and Hg1 sec tions) com pos ing this a ma rine fauna, has been doc u mented as transgressive. In east - suc ces sion. ern Tu ni sia, it is un der lain by a ma jor un con formity. It can di rectly We col lected a range of spe cies pres ent within the dif fer ent over lie con ti nen tal as well as ma rine Mio cene de pos its or the units. Ad di tion ally, we pro cessed (1) by ex trac tion of large spec - ma rine Plio cene, or even con ti nen tal Villafranchian de pos its. i mens of all taxa (larger than 2 mm in size) tak ing into ac count In the pres ent work we de tail the fos sil con tent of the MIS 5e their stratinomy and po si tion within the sed i ment, (2) by ex tract - and MIS 7 de pos its out crop ping along the Cap Bon Pen in sula ing 500 g of dry de pos its and gath er ing small spec i mens from and far ther to wards the south in the Hergla area. The fau nal spe - their res i dues ob tained in sieves (us ing a 1 mm mesh screen). cies dis tri bu tion and taphonomy are an a lysed. The main eco log i - All spec i mens that re mained on the screen were picked and cal char ac ter is tics of the dif fer ent in ver te brate spe cies com mu ni - iden ti fied and counted (Ta bles 1 and 2). Typ i cal spe cies as - sem blages are also de fined and any change in their as sem- blages com po si tion is de tected and com mented on. For tax o nomic iden ti fi ca tion and eco log i cal as sig na tion, we *Corresponding author, e-mail: [email protected] re ferred to Abbott (1960), Perrier (1954), Fekih (1975), Meco (1977) and Sessa et al. (2013). Tax o nomic at tri bu tions were Received: March 30, 2016; accepted: June 13, 2016; first published up dated by us ing the World Reg is ter of Ma rine Spe cies Da ta - online: September 12, 2016 Facies and fauna proxies used to reconstruct the MIS 5 and MIS 7 coastal environments in eastern Tunisia 187 green clay lay ers ob served only at Menzel Temime and (3) coarse sandy de pos its with dune cross-bed ding or densely packed root struc tures. Thus, to wards the top of this lower part a con ti nen tal char ac ter is de vel oped. The car bon ate unit is sig nif i cantly better de vel oped in the Cap Bon area as well as along the east ern coast of Tu ni sia. It con sists of 12 m of car bon ate de pos its, out crop ping at var i ous al ti tudes rang ing from 5 to 10 m above the pres ent sea level. It is com posed of two parts: 1. Centi metre- to metre-scale chalky sands rich in al tered ma rine mol lusc shells. These de pos its are or ga nized into four nor mally graded bed ding se quences un der lain by an ero sive sur face. This basal part re cords the ac tion of lo cal ep i sodic storms along this northeast ern coastal area. In this part are pre - served the main spe cies char ac ter iz ing the Sen e ga lese fauna, Persististrombus latus, a proxy of warm trop i cal ma rine wa ter. 2. Decimetric-scale car bon ate de pos its rich in ooliths and pel lets with dune cross-bed ding. This part con tains a con ti nen - tal in ver te brate fauna com posed mainly of helicid gas tro pods in clud ing He lix spp. and Rumina decollata. Lo cally, close to Qorba city, these helicids are as so ci ated with large mam mal spe cies: Phacochoerus aethiopicus, Gazella atlantica, Alcelaphus buselaphus, Equus mauritanicus, Ceratotherium simum and Hystrix cristata (Chakroun et al., 2005). To wards the south of Cap Bon, in the Sahel re gion close to the vil lage of Hergla (Fig. 1), there is an Up per Pleis to cene suc- ces sion that was stud ied by Mahmoudi (1988). This au thor dis - tin guished two for ma tions: the Kniss For ma tion and the Rejiche For ma tion, and he at trib uted this suc ces sion to the Tyrrhenian on the base of the oc cur rence of Persististombus latus (a se nior syn onym of Strombus bubonius). The basal part of the quartz-rich unit in the Hergla area (Hg1 and Hg2 sec tions) is equiv a lent to the Khnis For ma tion (Fig. 2). It is com posed from base to top of (1) fine sands, with rare crus- ta cean pel lets and ooliths, the fauna be ing rep re sented ei ther by de bris and small en tire bi valve shells, es pe cially cardiids and lucinids; (2) green clay and silts and (3) sandy de pos its with densely packed root struc tures. Fig. 1. Location map of the Tyrrhenian sites studied: The car bon ate unit that is equiv a lent to the Rejiche For ma- Menzel Temime, Qorba and Hergla tion is com posed of two parts: the lower part con sists of less or more con sol i dated car bon ate sands rich in molluscs and in clud - ing Persististrombus latus.

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